Electrolytic preparation of trialkoxyalkanes and tetraalkoxyalkanes



0, 1968 a. R. BELLEAU 3,

ELECTROLYTIC PREPARATION OF TRIALKOXYALKANES AND TETRAALKOXYALKANES Filed Oct. 1. 1965 VACUUM LINE HIGH BOILING RESIDUE KOH LUDGE VACUUM METHANOL DENSATE BRINE I |||||I II E II I I II I lIIIIIIIIIII IIIIMIIIIIIIII |I||l|: :|II

I m INVENTOR BERNARD R. BELLEAU ATTORNEYS.

United States Patent 3,415,725 ELECTROLYTIC PREPARATION OF TRIALKOXY- ALKANES AND TETRAALKOXYALKANES Bernard R. Belleau, Ottawa, Ontario, Canada, assignor to B. R. Belleau, Ltd., Ottawa, Ontario, Canada Filed Oct. 1, 1965, Ser. No. 492,118 11 Claims. (Cl. 20479) This invention relates to a new process for preparing certain trialkoxyalkanes and tetraalkoxyalkanes. More particularly, the invention relates to the production of a,a,,8-trialkoxyalkanes and a,a,fifi-tertaalkoxyalkanes from il-unsaturated ethers and an alkanol. These alkoxyalkanes have not previously been readily and economically preparable.

The invention is based on the discovery that lower ethers having a single ethylenic unsaturation in the 04,5- position relative to the ether group undergo anodic oxidation-dimerization in a lower alkanol containing a basic or neutral electrolyte with the production of a mixture of the above mentioned alkoxyalkanes. The reaction may be represented by the equation:

As the lower alkanol of the formula R OH, there may be used any alkanol of from one to four carbon atoms such as methanol, ethanol, l-propanol and l-butanol. The alkanol is employed in a considerable stoiclriometrical excess since it serves both as a solvent and as a reactant.

The unsaturated ether of the formula may be one of the lower members such as methyl vinyl ether or ethyl vinyl ether, which are currently preferred starting materials because of their cheapness and ready availability, or a member with up to about eight carbon atoms in the radicals provided that the ether possesses appreciable solubility in the alkanol. Thus suitable starting materials include l-butyl vinyl ether and methyl l-decenyl ether. Ethers in which the double bond is present in a ring, i.e., where R and R are linked together, such as ethyl l-cyclohexenyl ether, and ethers in which the oxygen is present in a ring, i.e., where R; and R are linked together such as Z-methylenetetrahydrofuran may be employed as also may ethers having both a double bond and an ether oxygen in the ring, i.e., where R and R are linked together, such as A -tetrahydrofuran or A -tetrahydropyran, and ethers having a cycloalkane ring but with both the double bond and the ether oxygen outside the ring, i.e., where R; and R are linked together, such as cyclohexylidenemethyl methyl ether.

The anodic oxidation-dimerization requires the presence in the reaction mixture of an electrolyte which must be inert to the reactants and reaction products. Generally, basic or neutral electrolytes serve satisfactorily while halides and acidic substances must be avoided. Examples of suitable basic electrolytes are the alkali and alkaline earth metal hydroxides and alkoxides, and the neutral or basic salts of such metals and of ammonium or the quaternary ammonium ion, e.g., a tetraalkyl ammonium ion. Suitable acid radicals for such salts include sulfate, perchlorate, acetate, carbonate, phosphate, trifluoroacetate, methanesulfonate and benzenesulfonate. The chosen electrolyte should be reasonably soluble in the lower 3,415,725 Patented Dec. 10, 1968 alkanol chosen as a reactant, about 0.2% be the practical lower limit for such solubility.

The anodic reaction is accomplished by passage a direct electric current between electrodes immersed in the reaction mixture, i.e., mixture of the unsaturated ether and electrolyte dissolved in the lower alkanol. The electrodes are preferably completely inert to the reactants and reaction products and as suitable anode or cathode materials there may be mentioned graphite or other electrically conductive forms of carbon, nickel, platinum, rhodium, palladium, gold, lead, plantinized titanium, boron carbide and tungsten carbide. Preferred electrode materials are nickel or graphite as the cathode and graphite, platinum, gold, boron carbide, tungsten carbide or platinized titanium as the anode.

The operating conditions for the anodic reaction are not critical. The highest reaction rates are accomplished by passing as much current as possible through the reactants while the unsaturated ether and/ or the lower alkanol are prevented from boiling 011? by the provision of adequate cooling. In most cases room temperature or lower is advantageous, although up to or is permissible in some cases. Stirring or other means of agitation are important for securing good reaction rates. The current may be obtained from any suitable source such as a 6-12 volt battery charger for small scale work, preferably one having a tapped or variable transformer. Current densities may generally be about 0.02 to 0.4 amp/cm. but this is not critical. The total amount of current passed in a batch operation should usually be somewhat in excess of the equivalent amount calculated from the reaction equation in order to insure completion of the reaction.

A suitable apparatus for batch operation consists of an electrolysis cell containing concentrically arranged anodes and cathodes, the cell being provided with a cold finger for cooling and a stirrer for agitation. For continuous operation a suitable apparatus is shown in the accompanying drawing which shows not only the electrolysis cell but also the product recovery stages. As shown in the drawing, the ethyl vinyl ether from reservoir 1 and a concentrated solution of potassium hydroxide in methanol from reservoir 2 are allowed to flow into a mixing chamber 3 via metering valves 4 and 5. Recovered methanol also flows into the mixing chamber from condenser 6. From the mixing chamber, the reactants flow into the top of the electrolysis cell 7 which is surrounded by a cooling jacket 8 through which cooling brine is circulated. The cell is also provided with a con denser 9 cooled by the same brine for avoiding reactant loss in the escaping hydrogen. The walls 10 of the cell are made of nickel and are connected to the negative side of a DC. electrical supply. Perforated graphite plates 11 electrically connected to each other by a graphite rod 12 and mounted with an inert insulating material 13 sealing them to the nickel walls are connected to. the positive side of the DC. supply. The reactants undergo anodic oxidation-dimerization in the cell and the products of reaction, that is l-ethoxy-1,2-dimethoxyethane and the dimer, 1,4-diethoxy-1,4-dimethoxybutane, dissolved in the excess methanol serving as solvent, pass through control valve 14 to first distillation column 15 for the recovery of methanol which is returned to the mixing chamber 3 via the condenser 6. From the base of this column the stripped product passes via a decanter 16 for removal of KOH sludge to a second column 17 for rectification of the low boiling fraction which is taken ofi as an overhead product and condensed by condenser 18 from which the liquid product passes into collector 19. The latter is connected to a vacuum line to maintain a pressure of about 10 mm. in column 17 and control valve 20 is used to regulate the input to the column. The high boiling product from this column is passed via a further decanter 21 for separation of KOH sludge to a third column 22 for rectification of the dimer fraction. The first and secand columns are heated by steam passed through jacket 23 while the higher temperatures necessary for rectification of the dimer are achieved by passing superheated steam through jacket 24. The dimer is collected as an overhead product and passes to condenser 25 from which the liquid dimer flows into collector 26 also connected to the vacuum line. High boiling residue is extracted from the last column via control valve 27.

The invention is further illustrated by the following examples in which a simple batch type apparatus employing either a platinum or a graphite anode and a nickel cathode was used. The glass cell was of 1 liter capacity and the reaction mixture was stirred in all cases.

EXAMPLE 1 1-ethoxy-1,2-dimethoxyethane and 1,4-diethoxy- 1,4-dimethxybutane A one liter electrolytic cell was charged with a solution of 42 g. of ethyl vinyl ether and g. of potassium hydroxide in 800 ml. of reagent grade methanol. The solution was electrolyzed for 24 hrs. at -5 to -l0 using an applied current of 4 amp. and 7 volts; the methanol was distilled at atmospheric pressure and recovered in greater than 90% yield. The residue was fractionated in vacuo through a Todd column to give a 68% yield of 1 ethoxy 1,2 dimethoxyethane, B.P. 58/27 mm. and IZD25=1.3954, and a 22% yield of 1,4-diethoxy-1,4-dimethoxybutane, B.P. 110/l0 mm. and n =l.4148. This fraction yields a 2,4-dinitrophenylhydrazone, M.P. 259262 (decom-p.).

Analysis.Calcd. for C l-L 0 C, 53.73; H, 10.44. Found: C, 53.26, C, 53.65; H, 10.41, 10.06.

Analysis-Calcd. for C H O C, 58.25; H, 10.67. Found: C, 58.58; H, 10.87.

Purity of the compounds was also ascertained by Vapor phase chromatographic analysis.

The same products are obtained in variable yields by substituting another suitable electrolyte or other suitable electrodes.

EXAMPLE 2 1,1,2-trimethoxyethane and 1,1,4,4-tetramethoxybutane The procedure of Example 1 was followed except that the ethyl vinyl ether was replaced by an equivalent weight of methyl vinyl ether. In this way, a 67% yield of 1,1,2- trimethoxyethane, B.P. 129130 C. and 11 =1.3918 and a 23% yield of 1,l,4,4-tetramethoxybutane, B.P. 96/l2 mm. and n :1.4136 was obtained.

Analysis. Calcd. for C H O C, 50.0; H, 10.0. Found: C, 49.84; H, 9.82.

Analysis.Calcd. for C H O C, 54.54; H, 9.09. Found: C, 54.14; H, 9.26.

EXAMPLE 3 l-n-butoxy-1,2-dimethoxyethane and 1,4-n-dibutoxy- 1,4-dimethoxybutane The procedure of Example 1 was followed except that the ethyl vinyl ether was replaced by an equivalent weight of n-butyl vinyl ether. In this way, a 75% yield of l-nbutoxy-1,2-dimethoxyethane, B.P. 79-8l/l2 mm. and n =1.4O63 and a yield of l,4-n'dibutoxy-l,2-dimethoxyethane, B.P. 92/0.3 mm. and I1D26:1.4242 was obtained.

Analysis. Calcd. for C H O C, 60.0; H, 10.0. Found: C, 59.61; H, 10.87.

Analysis.-Calcd. for C14H30O4I C, 64.14; H, 11.44. Found: C, 63.91; H, 10.94.

EXAMPLE 4 The procedure of Example 1 is followed except that the methanol is replaced by an equivalent quantity of another low molecular weight alcohol such as ethanol, n-propanol,

isopropanol, nbutanol, isobutanol, sec.-butanol. Thus, the use of ethanol under the conditions of Example 1 gave a 40% yield of 1,1,2-triethoxyethane, B.P. 83/30 mm. and n =l.4020, and 8% yield of l,l,4,4-tetraethoxyethane, B.P. l20125/30 mm. and n =1.4192.

EXAMPLE 5 The procedure of Example 1 is followed except that the vinyl ether is replaced by a cyclic a,,8-unsaturated ether such as A -tetrahydropyran, A -tetrahydrofuran, A hexahydrooxepin or their analogs carrying lower alkyl substituents on the rings. Thus, the use of 84 g. of A tetrahydropyran and electrolysis for 40 hours at 4.0 amp. at 5, gave a 66% yield of a mixture of cisand trans- 2,3-dimethoxy-tetrahydropyran, B.P. 85/28 mm. and 11 9 14351, and 24% yield of 2-methoxy-3-(2-methoxy-3'-tetrahydropyranyl)-tetrahydropyran as a mixture of configurational isomers, B.P. 1l8/1.5 mm. and 11 1.4684.

A/zalysis.-Calcd. for 0 1-1 0 C, 57.53; H, 9.58. Found: C, 56.96; H, 9.23.

AnaIysiS.-Calcd. for C H O C, 62.60; H, 9.56. Found: C, 62.50; H, 9.16.

EXAMPLE 6 The procedure of Example 1 was followed except that the ethyl vinyl ether was replaced by an equivalent weight of l-ethoxycyclohexene. In this Way a 66% yield of 1- ethoxy-l,Z-dimethoxycyclohexane, B.P. 59/1 mm. and 11 14408 was obtained. The high boiling residue was not worked up for recovery of any dimer.

Analysis.-Calcd. for C H O C, 63.82; H, 10.63. Found: C, 63.75; H, 10.05.

EXAMPLE 7 The procedure of Example 1 was followed except that the ethyl vinyl ether was replaced by an equivalent weight of methyl l-decenyl ether. In this way there was produced a 40% yield of 1,1,2-trimethoxydecane, B.P. 97/1 mm. and 11 14288. The reaction products were not worked up for recovery of any dimer.

Analysis.Calcd. for C I-E 0 C, 67.24; H, 12.06. Found: C, 66.74; H, 11.51.

The products produced in accordance with the invention are useful as solvents or as chemical intermediates. The solvent properties of the trialkoxy compounds, particularly the simpler members, are comparable to or better than those of known solvents of the oxygenated type such as 1,2-dimethoxyethane. Furthermore the trialkoxy compounds can be polymerized to polyacetals, hydrolysed to alkoxyaldehydes or cracked to 1,24iialkoxyethylenes which themselves can be polymerized to poly(alkoxyethylenes). The tetraalkoxy compounds (dimers) may be used as flotation agents in many cases, e.g. tetraethoxybutane; may be cracked to yield 1,4-dialkoxybutadienes Which may be polymerized to rubber-like compounds; may be reacted with pentaerythritol or the corresponding tetramine to give synthetic resins; or may be hydrolysed to dialdehydes. The last mentioned compounds are useful intermediates for the production of tropinones, and, like glutardialdehyde, can also be used as cross-linking or tanning agents.

What I claim as my invention is:

1. A process for converting u,fi-unsaturated ethers into ot,0c,B trialkoxyalkanes and oc,cc,5,5 tetra alkoxyalkanes which comprises subjecting the a e-unsaturated ether to anodic oxidation in solution in a lower alkanol and in the presence of a dissolved inert basic or neutral electrolyte.

2. A process as claimed in claim 1 wherein the 43' unsaturated ether is a compound of the formula wherein R is an alkyl group of from 1 to 8 carbon atoms,

or a 5 or 6 membered cycloalkyl radical, and R R and R are hydrogen or alkyl groups of from 1 to 8 carbon atoms.

3. A process as claimed in claim 1 wherein the 41,6- unsaturated ether is a compound of the formula wherein R and R are hydrogen or an alkyl group of 1 to 8 carbon atoms and R and R together represent an alkylene group of from 2 to 5 carbon atoms.

5. A process as claimed in claim 1 wherein the 11,13- unsaturated ether is a compound of the formula wherein R is an alkyl group of from 1 to 4 carbon atoms,

and wherein the lower alkanol is methanol or ethanol.

6. A process as claimed in claim 1 wherein the afiunsaturated ether is a compound of the formula wherein R is an alkyl group of from 1 to 4 carbon atoms and R is an alkyl group of from 1 to 8 carbon atoms, and wherein the lower alkanol is methanol or ethanol.

7. A process for the production of 1,1,2-trimethoxyethane and 1,1,4,4-tetramethoxybutane which comprises subjecting a methanolic solution of methyl vinyl ether and an alkali metal hydroxide or methoxide to anodic oxidation and recovering the 1,1,2-trimethoxyethane from the electrolysis product.

8. A process for the production of 1-ethoxy-1,2-dimethoxyethane and 1,4 diethoxy 1,4 dimethoxybutane which comprises subjecting a methanolic solution of ethyl vinyl ether and an alkali metal hydroxide or methoxide to anodic oxidation and recovering the 1-eth0xy-1,2-dimethoxyethane from the electrolysis product.

9. A process as claimed in claim 7, wherein the electrolysis is carried out at or below about 25 C. with a nickel cathode and a platinum or graphite anode.

10. A process as claimed in claim 7, wherein the methanolic solution contains about 5 to 10% by weight of the vinyl ether and 0.5 to 1% of potassium hydroxide, and is electrolysed between graphite anode and a nickel cathode at about -5 to -10 C. using an applied DC voltage of about 6 to 12 volts at a current of about 2 to 8 amps.

11. A process for the continuous production of (1,04,13- trialkoxyalkanes and a,a,5,5 tetraalkoxyalkanes which comprises continuously passing a lower alkanolic solution of an u, 3-unsaturated ether and an inert, neutral or basic electrolyte to an electrolysis zone, subjecting said mixture to electrolytic oxidation, stripping lower alkanol from the electrolysis product, distilling off the trialkoxyalkane from the stripped reaction product, and distilling off the tetraalkoxyalkane from the residual stream.

References Cited UNITED STATES PATENTS 3,296,225 1/1967 Worrall 20480 3,313,717 4/1967 Kuwata et a1. 20478 3,326,784 6/1967 Koehl 20480 HOWARD S. WILLIAMS, Primary Examiner. H. M. FLOURNOY, Assistant Examiner. 

1. A PROCESS FOR CONVERTING A,B-UNSATURATED ETHERS INTO A,A,B-TRIALKOXYALKANES AND A,A,$,$,-TETRA-ALKOZYALKANES WHICH COMPRISES SUBJECTING THE A,B-UNSATURATED ETHER TO ANODIC OXIDATION IN SOLUTION IN A LOWER ALKANOL AND IN THE PRESENCE OF A DISSOLVED INERT BASIC OR NEUTRAL ELECTROLYTE. 